1. Statement of the Technical Field
The inventive arrangements relate to handheld portable radios, and more particularly handheld portable radios that are intrinsically safe.
2. Description of the Related Art
Intrinsic safety refers to a condition of safety in a hazardous environment, particularly a hazardous environment in which explosive or flammable gasses may be present. Generally, this means that the device will not produce any spark or thermal effects under normal or abnormal conditions that will ignite a specified gas mixture. In fact, an instrument which is intrinsically safe is designed so that it will not cause any type of ignition in any form under normal or abnormal operating conditions, including fault conditions. Standard setting bodies offer approvals and/or certification marks for equipment which can be shown to intrinsically safe in accordance with certain standards. One such approval standard that is well known is FM 3610 as promulgated by FM Approvals LLC. The FM 3610 standard was amended in January 2010.
Design of a handheld portable radio to achieve an intrinsically safe certification compliant with the FM 3610 standard can be a formidable task. The amended standard of Jan. 10, 2010 sets forth thermal requirements and spark ignition requirements which are more stringent than those in the past. Complying with these requirements in a relatively small form factor device is very challenging. In fact, it is generally accepted that the trade-offs required to achieve certification are likely to affect key radio performance parameters such as output power, battery life, and received audio power, to name a few.
Evidence of the degraded radio performance resulting from complying with intrinsically safe standards fact can be found in radios that meet the ATEX standard. The ATEX standard has been in place in the European Union since 2003 for protecting workers from potentially explosive atmospheres. Radios that meet the ATEX standard are typically lower output power and are not multi-mode. The new FM 3610 standard is not yet implemented in North America, and it remains unclear at this time whether manufacturers will be able to maintain existing levels of handheld radio performance without reducing transmitter output power.